feat(invariants): implement package runtime checks

packages/sdk/helper/src/invariant.ts

@@ -1,14 +1,8 @@
-/**
- * Generated invariant ownership companion for `@deepseek-ai/dsh-helper`.
- * Replace this file with package-owned checks while preserving its registration.
- *
- * @generated scripts/gen-package-invariants.ts
- * @module @deepseek-ai/dsh-helper/invariant
- */
+/** Package-owned runtime contracts for @deepseek-ai/dsh-helper. @module @deepseek-ai/dsh-helper/invariant */
 
 /* jscpd:ignore-start */
 import type { Context } from 'cordis'
-import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+import { assertInvariant, type InvariantInstaller } from '@deepseek-ai/dsh-invariants'
 
 const PACKAGE_NAME = '@deepseek-ai/dsh-helper'
 
@@ -17,8 +11,22 @@ export const name = 'helper-invariant'
 /** Services required before the companion can register. */
 export const inject = ['invariants']
 
-/** Reserve this package's invariant ownership until it adds relational checks. */
-const install: InvariantInstaller = () => {}
+/** Assert FeatureId's zero-cost representation and boundary validation. */
+const install: InvariantInstaller = (ctx, fail) => {
+  ctx.effect(async () => {
+    const { featureId } = await import('./ids.ts')
+    assertInvariant(fail, featureId('local-plugin') === 'local-plugin',
+      'a valid feature id must preserve its runtime string value')
+    let rejected = false
+    try {
+      featureId('Invalid Feature')
+    } catch (error) {
+      rejected = error instanceof Error
+    }
+    assertInvariant(fail, rejected, 'feature ids must reject values outside lowercase kebab-case')
+    return () => {}
+  }, 'dsh-helper: validate feature identities')
+}
 
 /**
  * Register this package's invariant companion.